Understanding anatomical plasticity of Argan wood features at local geographical scale in ecological and archaeobotanical perspectives

Abstract

The emergence of the Argan tree as an agricultural, pastoral, cultural, economic and ecological keystone species in Southern Morocco is considered to be linked to the settlement of agropastoral communities that favored its expansion. Nevertheless, the use and exploitation of Argan tree is documented by both few medieval written sources and archaeobotanical studies, from a single location, Îgîlîz (Toughmart, Morocco), a famous medieval site of the Anti-Atlas Mountains. Therefore, data remain scarce regarding the type of Argan communities exploited at this period. In order to document this question, a quantitative eco-anatomical approach aiming to understand variations of wood characters involved in sap conduction and reserve storage, is developed from modern samples collected in the area of Îgîlîz. Results show that diameter of branches and environmental factors are the major parameters explaining plasticity of wood anatomical characters. Quantitative eco-anatomical features of Argan archaeological charcoal confronted to two statistical models, allow assessing both the diameter of the branches from which it derives and the agro-ecological conditions of tree growth and development. This preliminary study may be considered as a relevant and pioneering work for the understanding of the eco-history of the Argan tree, and of its use and exploitation during the past.

Resisting Aridification: Adaptation of Sap Conduction Performance in Moroccan Wild Olive Subspecies Distributed Over an Aridity Gradient

“…For these populations, mainly distributed in Northern Morocco and characterized by a matorral-type vegetation, a compromise between SVS and DVS has allowed the tree to maintain a relative constant sap conductance and thus water supply. An overall increase in the size of vessel related to the age of the vascular cambium has already been recorded in other species with a distinct wood structure, such as Mediterranean evergreen oaks (holm oak, Quercus ilex, and cork oak, Quercus suber-semiring porous wood) (Voulgaridis, 1990;Leal et al, 2007), grapevine (Vitis vinifera-ring porous wood) (Limier et al, 2018), and argan tree (A. spinosa-diffuse porous wood) (Ros et al, 2021).…”

“…In trees, an increase in the size of the vessel was globally linked to the increasing volume of plant parts to be fed by sap, namely the axial apices and the leaves of the last two or more rarely three growth-units (Choat et al, 2012). In this way, the growth and tree development and consequently the cambial function appeared to lead to an overall increase in the amount of conducting tissue (Steppe et al, 2015;Ros et al, 2021). Moreover, with the increased age of the branch, the vascular cambium seemed generally to provide a wood with a lower DVS and of lesser density, from a mechanical point of view.…”